import org.w3c.dom.ls.LSInput;

import java.util.concurrent.ScheduledExecutorService;

// 1、无头单向非循环链表实现
class SingleLinkedList {
    static class ListNode{
        public int val;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;

    //头插法
    public void addFirst(int val){
        ListNode node = new ListNode(val);
        node.next = head;
        head = node;
    }
    //尾插法
    public void addLast(int val){
        ListNode node = new ListNode(val);
        if(head == null){
            head = node;
            return;
        }
        ListNode cur = head;
        while (cur.next != null){
            cur = cur.next;
        }
        cur.next = node;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int val){
        try {
            checkIndex(index);
        }catch (IndexNotLegalException e){
            e.printStackTrace();
        }
        if(index == 0){
            addFirst(val);
            return;
        }
        if(index == size()){
            addLast(val);
            return;
        }
        ListNode cur = findIndexSubOne(index);

        ListNode node = new ListNode(val);
        node.next = cur.next;
        cur.next = node;
    }

    private void checkIndex(int index) throws IndexNotLegalException{
        if(index < 0 || index > size()){
            throw new IndexNotLegalException("index不合法！");
        }
    }

    private ListNode findIndexSubOne(int index){
        int count = 0;
        ListNode cur = head;
        while(count != index-1){
            cur = cur.next;
            count++;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int val){
        ListNode cur = head;
        while(cur != null){
            if(cur.val == val){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int val){
        if(head == null){
            return;
        }
        if(head.val == val){
            head = head.next;
            return;
        }
        ListNode cur = head;
        while(cur.next != null){
            if(cur.next.val == val){
                ListNode del = cur.next;
                cur.next = del.next;
                return;
            }
            cur = cur.next;
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int val){
        //1. 判空
        if(this.head == null) {
            return;
        }
        //2. 定义prev 和 cur
        ListNode prev = head;
        ListNode cur = head.next;
        //3.开始判断并且删除
        while(cur != null) {
            if(cur.val == val) {
                prev.next = cur.next;
                //cur = cur.next;
            }else {
                prev = cur;//prev = prev.next;
                //cur = cur.next;
            }
            cur = cur.next;
        }
        //4.处理头节点
        if(head.val == val) {
            head = head.next;
        }
    }
    //得到单链表的长度
    public int size(){
        int count = 0;
        ListNode cur = head;
        while(cur != null){
            count++;
            cur = cur.next;
        }
        return count;
    }

    public void display(){
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    public void clear(){
        ListNode cur = head;
        while(cur != null){
            ListNode curN = cur.next;
            cur = null;
            cur = curN;
        }
        head = null;
    }

    public ListNode removeElements(int val){
        if(head == null){
            return null;
        }
        ListNode prev = head;
        ListNode cur = head.next;

        while(cur != null){
            if(cur.val == val){
                prev.next = cur.next;
            }else{
                prev = cur;
            }
            cur = cur.next;
        }
        if(head.val == val){
            head = head.next;
        }
        return head;
    }
}